Head,

Yeah there is a big difference. Not sure the make and model you are looking at but I have tested both Swarvos spotting scopes and both have benefits.
Angled scope has an rotating head and body so you can set it right on the bench with you and tip the angle towards your head. All you have to do to find your target is look left or right (depending if you shoot left or right handed)into the spotting scope and you are on target. It is however, a little more difficult to find your target in the field using the angled. Also, the angled are not to friendly with truck mounts.

Straight...well you have used the straight...no suprises there.